Don’t swallow that myth!
The New Scientist reports on six stubborn misconceptions about your health that you should definitely ignore
1 Sugar makes children hyperactive
EVERY parent has seen it happen: take a group of young children, add sugar, then stand back and watch them bounce off the walls. But although many parents will find it hard to believe, sugar does not cause hyperactivity.
A 1996 review of 12 blinded studies, where no one at the time knew which children had received sugar and which a placebo, found no evidence to support this notion. In fact, one of these studies concluded that the sugar effect is all in parents’ minds.
Parents and their 5- to 7-year-old “sugar-sensitive” children were split into two groups.
The parents of one group were told their children had been given a large dose of sugar, while the others believed their kids were in the placebo group. In reality, all the children had been given sugar-free food.
When the parents watched their offspring at play afterwards, those who thought their kids were in the sugar group were more likely to rate their behaviour as hyperactive.
Having said that, sugar does affect children’s brains, but in a surprising way. In one study, David Benton, a psychologist at Swansea University in the UK, found that in the half hour or so after having a glucose drink, 9- to 11-year-old school children were better able to concentrate and scored higher in memory tests. That is the opposite of hyperactivity, one characteristic of which is an inability to concentrate.
So perhaps what parents mistake for hyperactivity at parties is just kids focusing hard on having fun.
2 Drink eight glasses of water a day
IT is the myth that just will not go away. Almost everyone thinks they do not drink enough water, but the idea that we all should drink lots of it — eight glasses a day— is based on no scientific data whatsoever.
No one really knows where the eight-glasses idea comes from. Some blame the bottled water industry, but plenty of doctors and health organisations have also promoted it over the decades. The source might be a 1945 recommendation by the US National Research Council that adults should consume 1ml of water for each calorie of food, which adds up to about 2.5 litres a day for men and two litres for women.
What most people do not realise, though, is that we get a lot of that water from our food. Foods contain water and are broken down chemically into carbon dioxide and more water. So if you are not sweating buckets, you need only about a litre a day.
But any talk of glasses is misleading because there is no need to drink pure water. The fluids that people drink anyway, including tea and coffee, can provide all the water we need, says Heinz Valtin, a kidney specialist at Dartmouth Medical School in Lebanon, New Hampshire.
According to the myth, caffeinated drinks do not count because they are diuretic. Not true: a comparison of healthy adults in 2000 found no difference in hydration whether they got their water from caffeinated drinks or not.
3 Our bodies can and should be ‘detoxed’
WE live in a toxic world. You are breathing in lead as you read this. Your next meal will contain everything from natural poisons to pesticides and pollutants. As a result, the human body is a cesspit of suspect chemicals.
What can we do about it? According to popular wisdom, we need to “detox” to get rid of these poisons, and there is no shortage of advice on the best way to accomplish this. But do any of these detox plans work? And is detoxing really good for us?
We are already doing it all the time with the help of our livers, kidneys and digestive systems. Most of the toxic chemicals we consume are broken down or excreted, or both, in hours.
However, it can take weeks, months or even years to get rid of some substances, especially fat-soluble chemicals such as dioxins. If we take these in faster than our bodies can get rid of them, levels build up.
Many detox programmes promote a period of consuming only fluids and no solid food but this will make virtually no difference to levels of chemicals that have built up over years. “For many of these, it will take between six and 10 years of zero exposure to get rid of half of the amount stored in our fat tissues,” said Andreas Kortenkamp, a toxicologist at Brunel University in London. “That is not achievable because, unfortunately, there is no zero exposure.”
Fasting or dieting releases fat-soluble chemicals into the blood, rather than eliminating them. That said, you can reduce your exposure to toxic chemicals, like nicotine and alcohol.
4 Being a bit overweight shortens life
LET us be clear: being seriously obese is bad for your health.
A body mass index of over 40 increases the risk of type-2 diabetes, heart disease and certain cancers, and increases the risk of dying from any cause by up to 29%. This is not a health myth. But carrying just a few extra kilograms, far from being a oneway ticket to an early grave, seems to deter the grim reaper, according to a recent review of nearly 100 studies involving nearly three million people.
The review, led by Katherine Flegal of the US Centres for Disease Control in Hyattsville, Maryland, reported this year that being “overweight”— defined as having a body mass index (BMI) of 25 to 29 — seems to have a protective effect, with a 6% reduction in death risk compared with people with a BMI of between 18.5 and 25.
Those with a BMI of over 35, however, have a higher risk.
It is not clear why being overweight might protect against an early death.
Perhaps carrying a few extra kilograms in reserve helps the body fight off illness or infection.
5 Antioxidant pills help you live longer
IT seems blindingly obvious: as our cells metabolise the food we eat, they produce rogue molecules called free radicals that wreak havoc.
Over a lifetime, the damage they do slowly builds up and may cause all kinds of degenerative diseases.
Luckily, though, many chemicals can act as antioxidants that mop up free radicals.
Plus, eating vegetables rich in antioxidants seems to reduce the risk of degenerative diseases. So popping pills packed with antioxidants must surely help stave off these diseases too?
That is what some scientists started thinking from the 1970s onwards. The Nobel prize-winning chemist Linus Pauling enthusiastically promoted high doses of vitamins without waiting for the evidence. The public lapped it up and a whole new industry sprang up to meet demand.
Then, in the 1990s, the results of rigorous trials of some of the most popular supplements, including betacarotene, vitamin E and vitamin C, started to come in.
Study after study has found that although these substances do work as antioxidants in the test tube, popping the pills does not provide any benefit.
On the contrary, some studies suggest that they are harmful.
A 2007 review of nearly 70 trials involving 230 000 people concluded that not only do antioxidant supplements not increase life span, but that supplements of betacarotene and vitamins A and E actually seem to increase mortality.
6 We should live and eat like cavemen
OUR bodies did not evolve for lying on the couch, watching TV and eating chips. So, the myth goes, we would all be a lot healthier if we lived more like our ancestors.
This “evolutionary discordance hypothesis” was posited in 1985 by medic S Boyd Eaton and anthropologist Melvin Konner, both of Emory University in Atlanta, Georgia. They claimed that although our genes have not changed for at least 50 000 years, our diets and lifestyles have since the advent of agriculture 10 000 years ago — and it all happened too quickly for us to evolve to deal with it. This, they said, is why diabetes, heart disease and cancers are rife. If we exercised more and ate like huntergatherers, we would be healthier.
The Stone Age or “paleo” diet based on these ideas has become popular. It involves eating game, fish, fruit, vegetables and nuts, and avoiding grains, dairy, legumes, oils, refined sugars and salt. Some aspects, such as exercising more and eating less highly processed grains and sugars, agree with the latest evidence. But others, such as ditching grains, legumes and dairy, do not. And the underlying rationale is flawed.
The idea that there was some evolutionary sweet spot 50 000 years ago just is not true, said Marlene Zuk, an evolutionary biologist at the University of Minnesota. Our ancestors were not perfectly adapted to their lifestyles, and we have adjusted to our agricultural diet.